1. Field of the Invention
This invention relates to a cryosurgical instrument.
2. Description of the Prior Art
In U.S. Pat. Nos. 3,696,813 and 4,018,227 assigned to the same assignee as the present invention, a cryosurgical instrument operating on the Joule-Thomson refrigeration principle is disclosed. Gas under pressure is transported through a narrow orifice to a tip and expanded, cooling the tip. The tip is contacted with tissue to perform various surgical techniques, amongst which are retina attachments or weldments, and other ophthamological procedures. By closing a valve to preclude exhaust of the pressurized gas, back pressure is created in the tip to warm or defrost the tip once the surgical procedure is completed.
With the advent of larger tips for performing such surgical procedures, the inlet and exhaust gas line tubing have had to be increased in diameter to effect sufficient freezing and defrost. This in turn has led to difficulty in manipulating and rotating the tip during surgery, particularly, to place the tip at a proper angle to the eye to perform the required surgery, because the increased diameter tubing is stiffer, opposing ready movement of the tip connected to it.
Accordingly, this invention provides a rotatable tip construction in a cryosurgical instrument operable by a Joule-Thomson expansion of gas through the tip. By providing a rotatable tip, the tip may be properly positioned to perform a particular surgical technique, regardless of the shape of the tip or degree of stiffness of the gas inlet and exhaust lines connected to the tip which tends to oppose ready manipulation thereof.